Autumn – The Season of Soil Prep

The leaves rustle in the wind, the gold and fire-red hues dance around and dazzle us before falling back to Earth, oh so delicately. Attention shifts from swimming and sun tanning to drinking mugs of hot tea after a day searching for the perfect carving pumpkin. Yes, this is the glorious season of Autumn. To the surprise of many, it’s also one of the most important times of year for the garden! If we are to manage the land (and our time) strategically, we must capture the benefits of rain and cold and time so we can work less during the rest of the year.

Let us return to the image of leaves falling on the ground. It’s such a dazzling display of nature – and one of my favorite things to see – but it’s also the trees’ way of teaching us how to manage soils. You see, those trees are doing a few things: feeding themselves, protecting their roots from cold, winter frosts by mulching themselves heavily with their now dead and dying leaves, and providing essential habitat for the predators that will hopefully fight off invaders the following year. When we take away the tree’s leaves, we deprive the roots of their winter coats. But why in Autumn? By allowing the leaves to sit and rot for almost 2 seasons (late Autumn – early Spring) we allow the leaves to decompose which in turn adds nutrition to the soil. Mulching in autumn also disallows weeds to germinate at the rate in which weeds germinate in uncovered soil. Any clever weeds that break through the mulch layer are impressively easy to pull up. Mulch protects soil organisms from UV radiation, preserves water, helps water infiltration, and hosts many overwintering critters and insect eggs, such as salamanders, chipmunks, toads, moths, and butterflies. The list could go on..

Here at Fiddle, we have decided to try a few different styles of mulching. I will be covering a large area of the garden with leaf mulch, plus leaving all of my leftover annuals to decompose in the field over the winter. The rest of the beds are going to be mulched with wood chips, which is often not considered a viable annual garden mulch. The common concern with wood chips is they will tie up nitrogen in the soil, which is why we never would till them in. In my observations, the nitrogen issue only occurs at the very surface where the soil and woodchips meet. In my first year of laying down chips I simply do not direct sow seeds in the chip mulch. Laying down manure between the soil and chips also seems to give the chips extra nitrogen to break down without depleting from the soil below. Transplanting in the PNW climate is often necessary for certain plants, so it isn’t particularly inconvenient for us to not direct sow in some areas. I am also careful the first year or two to still mix in a bit of compost or worm castings into each hole I plant to ensure the plants have enough to eat. As time progresses, the chips break down and feed the soil an incredible compost tea every time it rains or is watered. The soil then becomes rich with vitamins and minerals brought up both from the chipped tree’s taproots (which is then redistributed back to surface of the soil as the chips decompose), as well as a healthy ecosystem of decomposers working hard to make nutrition available. A well mulched bed (4-6 inches) should take care of the garden for at least 5 years! Adding a few inches of woodchips every 5 years and light layer of manure each season seems like nothing when you compare it to the tillage and amendment application most conventional organic farmers perform each year.

Below I’ve written a brief description of how we will prepare beds this autumn for spring planting. I’ve borrowed most of these ideas from many farmers and gardeners. Feel free to borrow them yourself.

Method 1: Wood Chip Mulch

(Optional – mainly done if highly resilient species are present) Solarize the area using leftover greenhouse plastic / any clear plastic sheets you have lying around. Don’t have plastic? Secure a brown or black tarp down on all sides for 2 weeks for a light deprivation kill.*

Add any soil amendments your site might need, especially if it has been previously unmulched. This step might eventually become unnecessary as you observe your soil health improve.

Lay down a layer of newspaper about 6 sheets thick to suppress any further germination on your site.

Lay down a 2-3 inch layer of nitrogen rich manure. Hot is fine if using on shrubs and trees. Be sure to use cold or semi-composted manure on areas where annuals will be planted the following year.

Lay down a 4-6 inch layer of wood chips for annual beds, or a 8-10 inch layer of wood chips around trees and shrubs.

Water the area well.

Water in some compost tea that is rich in microbial life. Feel free to inoculate your wood chips with King Stropharia (Stropharia rugosoannulata)or Oyster Mushroom (Pleurotus ostreatus) mycelium for extra harvests in your garden!

Let it sit mostly fallow for at least 6 months. Occasionally water in some compost teas for biological health.**

Once a year, add a light dusting of composted chicken manure on top of your chips for an extra nitrogen boost. You may also add a light layer of leaf mulch each autumn. Always layer on top of the chips rather than till under.

*If you are worried about ultra compacted soil not being fluffy enough in the spring, your first step might be a light tillage or broadforking. This would be the only time you would till this area. Solarize AFTER you till to suppress any seed germination from the tilling, then complete the rest of the steps. If you do end up tilling, be sure to add plenty of compost tea rich in biochar and microbes throughout the season.**Why add biological teas? Think about how we treat our bodies after they have become sick or weak, we add plenty of healthy nutrients and probiotics to give us an upper hand towards health. Treat any non mulched, plowed soil or lawn as if it had been ill and is now healing.

Method 2: Leaf Mulch

Add a light layer composted manure for an extra nitrogen boost in the garden (i.e. compost chicken or horse manure) and any amendments your site might need, especially if your garden has previously been farmed unmulched.

Spread them around your garden. Make an effort to add the leaf mulch underneath any living foliage. If you have enough leaves, feel free to pile them up a foot thick. Try to fluff them up a bit when laying down so they don’t lay in a flat pile as that might create an anaerobic matting that could hurt your soil biology.

Throughout the season consider adding compost teas rich in biology for added soil health.

Let sit fallow – you will be amazed at your soil come spring! Simply brush the leaves aside where you want to plant and direct sow or transplant. No need to remove the leaves entirely. They will continue to break down and hold in moisture for the remainder of the season.

Thanks for reading! Stay tuned for our next post about making rich and biologically active compost teas. In the meantime, sit back, relax, and let the soil do its thing. Cheers!